Removal of inorganic matter from petroleum residua



Aug. 29, 1950 E. M, HUGHES REMOVAL OF INORGANIC MATTER FROM PETROLEUM RESI DUA Filed Nov. 2'7, 1948 Mixer Concentrated Water Sulfuric Acid Mixer Rosiduum f r so 32 33 g 36; 37

' Flash I I l Tower -15 Figl' A Settling Tank Do-ushed Residuum Salt Water Vapor Flash Tower Filter De-oshad 4 Residuum I i 1 Salt I---- INVENTOI Q. EDWARD M. HUGHES BY ATTORNEYS the expense of the operation.

Patented Aug. 29, 1950 REMOVAL OF INORGANIC MATTER FROM PETROLEUM RESIDUA Edward M. Hughes, Chester, Pa., assignor to Sun 1 Oil Company, Philadelphia, Pa., a corporation of New Jersey Application November 27, 1948, Serial No. 62,371

4 Claims.

This invention relates to the treatment of petroleum residual oils for the purpose of removing inorganic matter and reducing the ash content. The invention more specifically relates to a method of treating petroleum residua which contain alkaline naphthenates, whereby the naphthenates are neutralized and the resulting salt is obtained in the form of relatively large crystals which may readily be separated from the treated oil.

In refinery practice it is customary to subject the crude petroleum to a topping operation wherein the lower boiling fractions such as gasoline, kerosene and gas oil are distilled off and then to treat the reduced crude with an alkali, such as caustic soda, preliminary to subjecting it to further distillation under vacuum to remove the lubricating oil fractions. Treatment of the reduced crude with alkali converts any naphthenic acids which are present into alkaline naphtenate soaps. In the subsequent vacuum distillation step the alkaline naphthenates do not distill but rather remain in the bottoms or residuum from the operation in admixture with high boiling hydrocarbons and asphaltic material.

Consequently, the residuum product will have a high ash or inorganic content which reduces its value for use as fuel oil. For example, in the practice of a process of this type such as described in Pew Patent No. 1,761,153, it has been found that crude petroleum of the naphthenic base type will yield a residuum having an ash content generally of the order of 2-3%. However, when the residuum is utilized as fuel oil, it is necessary or desirable that it have an ash content below 0.20% and preferably below 0.10%. Some means of de-ashing the residuum is therefore necessary in order to render it fit for commercial use as a fuel.

While various proposals have been made for reducing the inorganic content of residual stocks,

the diificulty or expense involved in practicing the proposed methods commercially has limited their usefulness. Removal of the inorganic matter is complicated by the fact that such residual oils have great emulsion-forming tendency, even after the alkaline naphthenate soaps have been converted by means of mineral acid into naphthenic acids and inorganic salt. Consequently, neutralization of the soaps followed by extraction of the saltwith water has been found to be more or less unsuccessful. Water extraction of the salt may be accomplished in some instances by employing selected deemulsifying agents but this adds to According to the present invention, the inorganic content of a petroleum residuum which contains alkaline naphthenates is effectively reduced by treating the residuum with sulfuric acid in the presence ofwater under certain conditions as hereinafter described, and then dehydrating the mixture, whereby the sulfate salt resulting from the neutralization of the naphthenates is obtained in the form of relatively large crystals. These crystals can then be separated readily from the treated residuum by gravity settling or filtration or in any other suitable or convenient manner.

Description of the invention will be made with reference to the accompanying drawings which are diagrammatic flowsheets illustrating two procedures for practicing the invention.

Referring first to Figure 1, the heavy residuum to be treated enters the system through line l0. A typical refinery product of this type, derived from naphthenic base crude, may have properties 'as follows:

S. U. vise. at 210 F.=3000-6000 A. P. I. gravity=l011 Ash content=2-3% in amount sufficient to neutralize or substantially neutralize the alkalinity or naphthenate soap content. It is preferable that the amount of acid used be at least sufficient to approach complete neutralization without exceeding the amount required for that purpose, but it is of course not necessary that exact neutrality be reached. Any part of the naphthenate soaps which is not neutralized will remain in the residuum during the subsequent steps of the process and will result in a higher ash content of the product.

The combined streams from lines I0 and I I pass into a mixing device 12 to insure effective mixing and neutralization. Mixer I2 is illustrated as an orifice type mixture, although any other suitable type of mixer may be employed. The mixture is maintained during the neutralization step under sufficient pressure to prevent vaporization of water, this being accomplished by means of a 3 back pressure relief valve H in the outlet flow line I3 from the mixer. It is important that the water he maintained in liquid phase during the neutralization step in order that the operation will result in the formation of salt crystals of relatively large size.

The next .step in the process comprises evaporating water from the neutralized residuum. Assuming that the residuum has entered the system at sumciently high temperature, evaporation of the water may be effected simply by reducing the pressure as by means of valve H1 and-directly introducing the mixture into a flash tower 15 from which water vapor passes off through overhead line 56. In cases where the temperature of the residuum is not sufiicient to cause vaporization of the water, .the residuum from mixer l2 first may be passed through a suitable heater (not shown) and then introduced into flash tower 15.

The dehydrated residuum gleaming the flash tower .throughline i3 contains salt crystals 10f relatiyely ilergsezsize .wh home-y beseparated .trom the residuum anys table manner, As shown in .Eigiuie 1., the .hot residuum may be sent to a settling tank .l;8 and therein permitted :to set- .tie forxsuuicient "time {to reduce the ash {content to the desired value. If desired, the-'hotiresiduum may be admixed with light fuel oil or other Ehy- .drocarbon fraction of relatively low :viscosity :beffore entering lsettlingtank J 3 order to accelerate .the rate of settling of the salt-particles, although this is not essential if the acidification .step has been carried @out under the conditions :above AZlBSOl bBd :a-nd the temperature in the settling tank is ;suiiicieritly high :to prevent :excessive viscosity. The 561,6-d3h'5d product may ;be i iithdrai f om tank :l-iv -;a.t ;an "upper ;level l9. Salt may -;removed from the, bottom inter nnittently zas hyoceasionally drawing off the de- .stantially exceeds 67 vthe resulting salt pargticles will ,be .of extremely fine form :so {that separation .by gravity will not take place :to any practical extent. Even when-the :prncess is praciticedwithafiltration 5136191111 place of the grayity settling, removal of the line salt particlesito the ,desired degree is difficult to achieve in commercial operation. n the other :hand, when sold .a strength substantially below -.6%% is 'gllfififi -d -culties .wilLbe encountered due tofozuning vwithin flash tower All: ,The acid strength thus should-lie wi-thin the range :of

l -Q 1hr weight and pref era ly should about Figure- 2 'strates a mod fied of. the IDROGES-Sdllhl n he ZYGSi'dllUEYljSIfiBSt.Tll'llXQdll h water ;and the with concentrated .sulfuric acid in amount sufficient {to substantially neutralize 1 1 Mil -the e sci-inspractioingzthe imzentie-n in ethis the proportion rOf water to sulfuric acid emploued should be such .as to .heequivalent to an acid strength .of de f-37% .xHflsQl'tby weight. 51in other words, if the water and sulfuric acid premixed with each other v:lee'fiore- :contacting cthe residuum, ithe resulting It appears that at least in some cases practice of the process according to Figure 2 is still more effective in securing a low ash content product.

Referring to Figure 2, water is introduced in the proper proportion through line 3| irito the hot residuum flowing in line and the two .are mixedin -mixer 32. The mixture flows through line 133 and meets a stream of concentrated sulfuric acid from line 34, the amount of acid being proportioned to substantially neutralize the alkaline naphthenates in the residuum. Mixing :is again effected by means of a second mixer 35. The neutralized mixture passes through line 36 and back pressure ,relief valve 3'! and thence to dash tower .38 from which water vapor is removed through overhead line 39. The dehydrated salt-containing residuum is withdrawn through line 4i} and, as illustrated in this case, may be sent to a filter 4| which separates the salt crystals and yields a product of low ash icon-tent. For commercial operation ,filter H sui s m or :be of he con inuous r ta y pre- -co y ioh iswell known to the art.

"EIZhe following examples are illustrative:

Example 1' illhe ;.petroleum residuum used in this example was obtained by treating a, reduced crude of naphthenic. base origin with caustic soda and then distilling off the lubricating oil fractions under vacuum. .-It had an .S. U. viscosity. at 210 F. of .3200. 2000 --g. of the residuum was heated to 200 and then was .mixedwi-th-fdofi of aqueous sulfuric acid having ,an H2504 oontentbf 6-5%,=this amount being required for approximately complete neutralization. The mixture was heated to about 00 under atmospheric pressure 'to effect dehydration. illhe dehydrated material Wasgpermittedzto Standpvernightat .a temperatureiof about 300 F. tojse parate thesalt crystals. The oil layer was tested io-r ash ,content, with results as follows:

Per cent Original ash content 2540 Ash content after settling overnight 0208 Another run .was made under similar conditions except that the H2SO4 content of .the aqueous sulfuric acidiemployed was 69.7%, .40.5 .ml. of the acid being employed tolapproximately neutralize .2000 g. of .the residuum.

,Per cent .Ash -con1ten t after settling overnight 1.55

TheseawsultsshoW that acid of.65% concentration was effective in producing salt crystals of relatively large size whereas acid of 169.7 concentration was ineffective for this purpose.

Example II Per cent Originalash content 2:40

summations-wouldhave :a strength or sau er /O. Ash content after settling 4 hrs. 0.08

As shown by the preceding examples, the process may be practiced either by adding the acid as an aqueous solution of proper concentration (60-67% HzSOr) or by first adding water and then concentrated acid in the proper proportions. It is not permissible, however, to add concentrated sulfuric acid, or acid having a concentration substantially above 67%, before the addition of the water, for this will result in the formation of such small salt crystals that separation by settling or filtration will be rendered impracticable.

Having described my invention, what I claim and desire to protect by Letters Patent is:

1. Method of treating petroleum residuum containing alkaline naphthenate-s to remove inorganic matter which comprises mixing the residuum at an elevated temperature with water and H2504 under suflicient pressure to maintain the water in liquid phase, the amount of H2SO4 employed being suflicient only to substantially neutralize the residuum and the proportion of water to H280; being equivalent to an acid strength of 60-67% H2SO4 by weight, said H2804 being added to the residuum not before the addition of the water, then vaporizing water from the residuum, thereby forming salt crystals of relatively large size, and separating said crystals from the treated residuum.

2. Method Of treating petroleum residuum containing alkaline naphthenates to remove inorganic matter which comprises mixing-the residuum at an elevated temperature with aqueous sulfuric acid having an acid strength of 60-67% H2504 by weight under sufficient pressure to maintain the water in liquid phase and in amount suificient only to substantially neutralize the residuum, then vaporizing water from the residuum, thereby forming salt crystals of relatively large size, and separating said crystals from the treated residuum.

3. Method of treating petroleum residuum contaming alkaline naphthenates to remove inorganic matter which comprises mixing the residuum at an elevated temperature with a small amount of water as hereinafter specified, then adding to and mixing with the residuum, while at an elevated temperature and under sufficient pressure to maintain the water in liquid phase, concentrated sulfuric acid in amount sufficient only to substantially neutralize the residuum, the proportion of total water to H2604 being equivalent to an acid strength of -67% H2804 by weight, then vaporizing water from the residuum,: thereby forming salt crystals of relatively large size, and separating said crystals from the treated residuum.

4. Method of treating petroleum residuum containing alkaline naphthenates and having an ash content in excess of 2.0% to remove inorganic matter which comprises mixing the residuum at a. temperature above 150 F. with aqueous sulfuric acid having an acid strength of about H2804 by weight under sufi'icient pressure to maintain the water in liquid phase and in amount suflicient only to substantially neutralize the residuum, then vaporizing water from the residuum, thereby forming salt crystals of relatively large size, and permitting the mixture to stand at a, temperature above F. fora time sufficient to settle out most of the salt and reduce the ash content of the residuum layer to less than 0.20%.

EDWARD M. HUGHES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,009,710 Goodwin July 30, 1935 2,434,528 Wadley Jan. 113, 1948 ,463,930 Wildman Mar. 8, 1949 

1. METHOD OF TREATING PETROLEUM RESIDUUM CONTAINING ALKALINE NAPHTHENATES TO REMOVE INORGANIC MATTER WHICH COMPRISES MIXING THE RESIDUUM AT AN ELEVATED TEMPERATURE WITH WATER AND H2SO4 UNDER SUFFICIENT PRESSURE TO MAINTAIN THE WATER IN LIQUID PHASE, THE AMOUNT OF H2SO4 EMPLOYED BEING SUFFICIENT ONLY TO SUBSTANTIALLY NEUTRALIZE THE RESIDUUM AND THE PROPORTION OF WATER TO H2SO4 BEING EQUIVALENT TO AN ACID STRENGTH OF 60-67% H2SO4 BY WEIGHT, SAID H2SO4 BEING ADDED TO THE RESIDUUM NOT BEFORE THE ADDITION OF THE WATER, THEN VAPORIZING WATER FROM THE RESIDUUM, THEREBY FORMING SALT CRYSTALS OF RELATIVELY LARGE SIZE, AND SEPARATING SAID CRYSTALS FROM THE TREATED RESIDUUM. 